In the chronically-instrumented dog (radiopaque implants in the right ventricular epicardium) we shall pusue the sophisticated mathematical analysis of the motion of the ventricular wall under acute volume and pressure overload. After the markers are implanted, the animals will be maintained for at least 3 weeks postoperatively before they are analyzed. They will be anesthetized and prepared for biplane x-ray data collection with the heart paced from a right intraventricular pacing catheter. With angiotensin infusion we will achieve acute pressure overload, and with dextran infusion we will obtain acute volume overload. In all these states the heart will be placed at the same rate (120 beats/min) while the marker motion is recorded with biplane high-speed cine-Roentgenography. Since the Roentgenographic and mathematical analysis explore the contracting and relaxing right ventricle as accurately as possible, the proposed rearch will lead to a better understanding of the normal ventricular function. We are convinced that this approach is capable of detecting the subtile changes that occur in early stages of hypertrophy. We shall gain insight into how the ventricle adapts regionally to demands of increased pressure and flow rate.